Trimmer mechanism for sewing machines



May 28, 1940.

B. P. PINKVOSS TRIMMER MECHANISM FOR SEWING MACHINES Filed March 11, 1939 Minus Patented May 28, 1940 UNITED STATES PATENT OFFICE TRIMMER MECHANISM FOR. SEWING MACHINES Berthold P. Plnkvoss, Bridgeport, Conn aleignor to The Singer Manufacturing Company, Elizabeth, N. .L, a corporation of New Jersey Application March 11, 1939, Serial No. 261,187 7 Claims. (Cl. 112-125) rler-arm facilitating throwing the trimmer-knife into and out of operation.

The invention consists in the knife-arm actuating mechanism hereinafter described in connection with the accompanying drawing which illustrates a preferred embodiment of the invention and in which:

Fig. 1 shows, in perspective, a sewing machine having the improved trimmer-actuating mechanism. Fig. 2 is an enlarged front elevation of the toggle-link connection between the knifedrlvlng bar and the knife-carrying arm, in the operative position of the toggle-links. Fig. 3 represents a view in side elevation of the knifearm actuating connections, the needle-reciprocating shaft and the knife-arm being shown in section. Fig. 4 represents a cross-section of the toggle connections on substantially the line 4-4 of Fig. 3. Fig. 5 is a detail view in side elevation of the toggle-link stop-plate. Fig. 6 represents a vertically transverse section of the knife-arm substantially centrally of the knife-arm lifting spring.

The sewing machine illustrated in the draw-- ing has the usual work-supporting bed-plate I, from one end of which rises the standard 2 of the bracket-arm 3 overhanging the bed-plate and terminating at its free end in a head 4. Rotatably journaledin the bracket-arm 3 is the needle-reciprocating shaft 5 (shown in Fig. 3) connected in any usual or suitable manner with the needle-bar 6 carrying at its lower end the needle I. The needle-bar 6 is journaled for vertical reciprocation in the usual feed-frame 8, in which is also journaled the feed-bar 9 carryihg at its lower end the feeding foot I0. Coopcrating with the needle land the feeding foot i is the presser-foot ll attached to the lower end ofthe presser-bar l2 movable vertically in the bracket-arm head 4.

The trimmer-mechanism includes the commercially well known knife-arm supporting-plate l3 secured in any usual or suitable manner upon the bed-plate l adjacent the arm-standard 2 and below the bracket-arm 3, said supporting-plate l3 being preferably adjustable in the usual or any suitable manner lengthwise of the bed-plate l. The supporting plate l3 has upstanding cars It spaced transversely of the bed-plate i, and pivotally mounted between said ears, as by suitable pintles, is ene end of an upwardly arched knifearm l5. Suitably secured upon the opposite end of the knife-arm i is a trimmer-knife l6 having its operative path of movement adjacent the needle I,

it being understood from the foregoing that the knife-arm l5 vibrates about an axis transverse to the axis of rotation of the needle-reciprocating shaft 5.

Intermediate its ends, the knife-arm l5 has vertically alined bosses I1 and it which are apertured to provide a socket, l9, Fig. 6. Slidably disposed in said socket I9 is a cupped thrust-tube having a rounded lower end adapted to engage the upper face of the bed-plate I under the action of a knife-arm lifting coil-spring 2|. When the knife-arm actuating mechanism is disabled, the spring it functions to swing the knife-end of the knife-arm l5 upwardly to an extent limited by a stop-screw 22, threaded into an upstanding ear 23 of the knife-arm and adapted to engage the bracket-arm standard 2 in the throw-out position of the trimmer-knife. This knife-arm mechanism is well known in the art and has therefore been herein described in general terms.

Carried by the needle-reciprocating shaft 5 is an actuating element in the form of an eccentric 24 rotatably disposed in a block 25 engaged by a fork 26 of a knife-driving bar 21. The forked bar 21 is guided for vertical reciprocation ina slot 28 provided in the front wall of the bracket-arm 3, said bar 21 being confined to right line reciprocation in said slot 28 by a retainerpiate 29 suitably secured upon the bracket-arm 3. A knife-driving bar of this general type is disclosed in the U. S. patent to' A. Rontke, No. 1,200,989, October 10, 1916.

Pivotally attached to the lower end of the knife-driving bar 21, by a shoulder screw 30, is one end of an upper toggle-link 3! which in its operative position depends generally vertically from the bar 21. Intermediate its ends, the link 3| has an apertured boss 32 into which is threaded a shoulder screw 33 pivotally attaching to the link 3| the upper end of a lower toggle-link 34, disposed adjacent the lower end of the link 3i. At its lower end, the link 34 is pivotally connected by a shoulder screw 35 to the knife-arm [5 adjacent the free end of said arm, it being understood that the pivot-screws 30, 33 and 35 are angular stop-plate 31 provided with a fingerpiece 33. The stop-plate 31 has a lateral extension 39 adapted to engage the lower toggle-link 34 thereby to determine the toggle-straightened operative position of the links 3|, 34. A bent spring 40 is secured by screws 4| to the stop-plate extension 39, said spring being adapted to yieldingly engage a shoulder 42 on the link 34, thereby yieldingly to latch together the links 3|, 34 in the operative position of said links.

It will be noted from Fig. 2 of the drawing that, in their operative position, the links 3|, 34 are relatively slightly inclined, i. e., the knuckle or pivot-joint between the two links is disposed slightly at one side of a straight line passing through the pivot-points 30 and 35. Consequently, in the downward movement of the knifedriving bar 21, the stop-plate extension 39 car-.

ried by the upper link 3| is forced into positive engagement with the lower link 34 and the two links together constitute a rigid thrust-bar free to swing about the pivot-screw connection 30 with the knife-driving bar. In the upward movement of the knife-driving bar 21, the spring 2| urges the knife-arm l5 upwardly and therefore functions to assist the latch-spring 40 in maintaining the pivotally connected links in their operative relationship.

' By a slight pressure against the left hand side of the finger-piece 38, the toggle may readily be broken, thereby disabling the knife-arm actuating mechanism and raising the knife-end of the knife-arm l5, as illustrated in dotted lines in Fig. 1 of the drawing. The upward swinging movement of the knife-arm is, of course, assisted by the spring 2| which further serves to hold said knife-arm yieldingly in its inoperative position. When bringing the toggle-links 3 34 again into their operative position, the free end of the knife-arm I5 is at the same time forcibly depressed by the straightening of the toggle-links, theknife-arm depressing power thus available being sufllcient to force the knife to sever work in the path of the knife, provided of course that the knife driving-bar 21 is at the lower end of its stroke.

Aside from the simplicity and effectiveness of the above described knife-arm actuating mechanism, a particular advantage resides in the fact that the toggle-link arrangement for throwing the knife-arm into and out of operation permits the hinge-joint 30 to be spaced a substantial distance from the knife-arm I5. In this connection, it is to be understood that, as the knife-arm I5 is a vibratory member, the thrust-bar which in the present case is constituted by the two togglelinks 3|, 34 has a sidewise swinging movement because of the pivotal connection of the link 34 with the knife-arm. Consequently, a sidewise thrust is imposed upon the knife-driving bar 21 which is largely minimized by spacing the hingejoint 30 a substantial distance from the knifearm and by connecting the link 3| to the bar 21 directly adjacent the guiding means for said bar 21. Furthermore, the above noted spacing of the hinge-joint 30 from the knife-arm provides for adjustment of the knife-arm lengthwise of the bed-plate without materially affecting the knife-arm actuating connections.

Having thus set forth the nature of the invention, what I claim herein is:

1. Trimmer mechanism for sewing machines comprising, a rotary actuating shaft, 9. t'rimmer knife carrier, an actuating member carried by said shaft, means operatively connected with said member for actuating said carrier including endwise reciprocable toggle-links, said links being relatively movable into and out of toggle-straightened operative position, and manually releasable means for holding said links in the operative position thereof.

2. Trimmer mechanism for sewing machines comprising, a trimmer-knife carrier, an actuating member, a toggle-link connection between said member and carrier, 9. stop determining a toggle-straightened operative position of said connection, and a latch for releasably holding said' connection in the operative position thereof.

3. Trimmer mechanism for sewing machines comprising, a vibratory trimmer-knife carrier, a reciprocatory actuating member, means for reciprocating said member, toggle-jointed links connecting said member and carrier, and manually releasable means for holding said links in substantial alinement for transmitting vibratory movements to said carrier from said member.

'4. Trimmer mechanism for sewing machines comprising, a pivotally mounted knife-carrier arm, a reciprocatory actuating member, means for reciprocating said member, toggle-jointed links pivotally connected to said member and arm, the pivotal axes of said links being disposed substantiaily parallel to the pivotal axis of said arm, a stop determining a toggle-straightened operative position of said links, and yielding means for releasably holding said links in said operative position.

5. Trimmer mechanism for sewing machines comprising, a trimmer-knife carrier adapted to be thrown into and out of operation, an actuating member, toggle-jointed links operatively connects ing said member and carrier in a toggle-straight-.

ened operative position of said links, stop means determining an inoperative position of said carrier in a toggle-broken position of said links, and means yieldingly urging said carrier into said inoperative position thereof.

6. In a sewing machine having a bed-plate, a bracket-arm overhanging said bed-plate and provided with knife-driving-bar guiding means, a rotary actuating shaft in said bracket-arm, an

actuating element carried by saidshaftQa knifedriving bar engaged by said actuating element and confined to right line vertical reciprocation by said guiding means, a trimmer-knife carrierarm pivotally mounted upon said bed-plate and adapted to be thrown into and out of operation, toggle-jointed links operatively connecting said knife-driving bar and said knife-carrier arm in 

